Electronic control circuits are used with internal combustion engines in order to optimize their operation under a variety of conditions. One component of such control circuits are "knock" sensor units which sense "knocking" or pre-ignition during engine operation and adjust various parameters such as timing and fuel mixture in order to minimize knocking. Knocking can be caused by a variety of factors including timing, fuel mixture, compression ratio, manifold pressure, exhaust back pressure, and fuel octane rating. Knocking is undesirable because it increases wear and decreases efficiency. A knock sensor unit uses one or more sensors to sense the vibrations caused by the knocking. The detecting of knocking is used to generate a signal which is used by the controller circuit adjust various engine parameters and reduce or eliminate the knocking. Typically more than one sensor is used on an engine to ensure accurate and reliable knock detection. Each sensor has associated with it its own signal conditioner channel for processing the signal before delivering it to the control circuit. Each channel requires a number of complex and expensive components: amplifier, rectifier, integrator, buffers, and sample and hold circuits. Multiple channels require multiple ports and accuracy requires that each channel be made exactly the same as the others in order to ensure that all signals are treated the same; otherwise the feedback controls will be distorted and engine performance will suffer. Typically one of the plurality of sensors will be best positioned to measure a given cylinder and only that sensor is monitored when the corresponding cylinder fires.